Video processor, display apparatus, and video processing method

ABSTRACT

A video processor includes a receiving section that receives video information representing video images and luminance-related information on the luminance of the video images and a video processing section that determines an expansion target luminance range of the video images based on the luminance-related information and expands the expansion target luminance range in such a way that the maximum luminance in the expansion target luminance range increases.

This is a Continuation of application Ser. No. 15/616,068 filed Jun. 7,2017, which in turn claims the benefit of Japanese Patent ApplicationNo. 2016-124817, filed Jun. 23, 2016. The disclosure of the priorapplications is hereby incorporated by reference herein in its entirety.

BACKGROUND 1. Technical Field

The present invention relates to a video processor, a display apparatus,and a video processing method.

2. Related Art

As a new method relating to video images, an HDR (high dynamic range)method has been known (see JP-A-2016-34125). In the HDR method, aluminance of 10000 nit is specified as the maximum luminance. It isnoted that 1 nit is 1 cd/m².

In an HDR display apparatus that supports the HDR method, the displaybrightness range corresponds to the range of luminance that HDR videoinformation compliant with the HDR method can take on (specifically,luminance range from 0 to 10000 nit). For example, an HDR displayapparatus, when displaying video images represented by HDR videoinformation, displays a video image portion having a luminance of 10000nit with the brightest white (brightest portion in display brightnessrange).

It is noted that all pieces of HDR video information do not representvideo images having the luminance of 10000 nit. For example, in theUHD-BD (ultra-high definition Blu-ray (registered trademark) disc)standard, the maximum luminance is limited to 1000 nit. Therefore, whenHDR video information representing video images having maximum luminancelower than 10000 nit is inputted to an HDR display apparatus, part ofthe brightness range of the HDR display apparatus, that is, thebrightness range portion corresponding to the luminance range from themaximum luminance of the HDR video information to 10000 nit is not used,and dark, low-contrast video images are therefore undesirably displayed.

SUMMARY

An advantage of some aspects of the invention is to provide a technologyfor broadening the luminance range of video images represented by videoinformation to increase the brightness of the video images.

An aspect of a video processor according to the invention includes areceiving section that receives video information representing videoimages and luminance-related information on luminance of the videoimages and a video processing section that determines an expansiontarget luminance range of the video images based on theluminance-related information and expands the expansion target luminancerange in such a way that maximum luminance in the expansion targetluminance range increases.

According to the aspect described above, since the expansion targetluminance range is so expanded that the maximum luminance in theexpansion target luminance range of the video images increases, thevideo images can be brighter and have higher contrast than in a casewhere the luminance range of the video images is not expanded. Further,since the expansion target luminance range is determined on the basis ofthe luminance-related information, the expansion target luminance rangecan be determined in accordance, for example, with the luminance of thevideo images.

In the aspect of the video processor, it is preferable that the imageprocessing section expands the expansion target luminance range in suchaway that the maximum luminance in the expansion target luminance rangeis equal to pre-specified target maximum luminance higher than themaximum luminance.

According to the aspect described above, since the maximum luminance inthe expansion target luminance range is converted into the pre-specifiedtarget maximum luminance higher than the maximum luminance, the maximumluminance in the expanded luminance range can be set at a fixed targetmaximum luminance. Therefore, for example, when the video informationhaving the expanded expansion target luminance range is inputted to thedisplay section, and the target maximum luminance is set at the maximumin the luminance range that the display section can handle, thehighest-luminance video image portion of the video images can bedisplayed by using the brightest portion in the brightness range ofdisplay operation performed by the display section. The video images cantherefore be brightest possible video images.

In the aspect of the video processor, it is preferable that the imageprocessing section lowers the maximum luminance in the expansion targetluminance range by a greater amount when luminance represented by theluminance-related information is lower.

According to the aspect described above, the lower the luminancerepresented by the luminance-related information, the lower the maximumluminance in the expansion target luminance range, and the maximumluminance is converted into the pre-specified target maximum luminance.Therefore, the lower the luminance represented by the luminance-relatedinformation, the higher the degree of increase in the maximum luminancein the expansion target luminance range.

In the aspect of the video processor, it is preferable that theluminance-related information is maximum luminance informationrepresenting maximum luminance of the video images.

According to the aspect described above, the expansion target luminancerange can be determined in accordance with the maximum luminance of thevideo images. In the HDMI (high-definition multimedia interface(registered trademark)) standard, the maximum luminance information iswritten in Info Frame. The receiving section can therefore readilyreceive the maximum luminance information by receiving Info Framecompliant with the HDMI standard.

In the aspect of the video processor, it is preferable that theluminance-related information is maximum average luminance informationrepresenting a maximum of average luminance values of frames that formthe video images.

According to the aspect described above, the expansion target luminancerange can be determined in accordance with the maximum of averageluminance values of the frames that form the video images. In the HDMIstandard, the maximum average luminance information is written in InfoFrame. The receiving section can therefore readily receive the maximumaverage luminance information by receiving Info Frame compliant with theHDMI standard.

In the aspect of the video processor, it is preferable that theluminance-related information is point-of-editing maximum luminanceinformation representing maximum luminance of light from a displayapparatus used when the video images are edited.

According to the aspect described above, the expansion target luminancerange can be determined in accordance with the maximum luminance oflight from a display apparatus used when the video images are edited. Inthe HDMI standard, the point-of-editing maximum luminance information iswritten in Info Frame. The receiving section can therefore readilyreceive the point-of-editing maximum luminance information by receivingInfo Frame compliant with the HDMI standard.

In the aspect of the video processor, it is preferable that thereceiving section receives the luminance-related information formed of aplurality of types of luminance-related information, and that the imageprocessing section determines the expansion target luminance range foreach of the pieces of luminance-related information and expands one ofthe expansion target luminance ranges for the pieces of theluminance-related information, an expansion target luminance rangehaving lowest maximum luminance, in such a way that the maximumluminance in the expansion target luminance range having the lowestmaximum luminance increases.

According to the aspect described above, the video images can bebrighter and have higher contrast than in a case where the imageprocessing section expands one of the expansion target luminance rangesfor the pieces of luminance-related information, an expansion targetluminance range having the highest maximum luminance, in such a way thatthe maximum luminance in the expansion target luminance range increases.

In the aspect of the video processor, it is preferable that thereceiving section receives the luminance-related information formed of aplurality of types of luminance-related information, and that the imageprocessing section determines the expansion target luminance range foreach of the pieces of luminance-related information and expands one ofthe expansion target luminance ranges for the pieces of theluminance-related information, an expansion target luminance rangehaving highest maximum luminance, in such a way that the maximumluminance in the expansion target luminance range having the highestmaximum luminance increases.

According to the aspect described above, luminance saturation due to theexpansion of the luminance range can be suppressed as compared with acase where the image processing section expands one of the expansiontarget luminance ranges for the pieces of luminance-related information,an expansion target luminance range having the lowest maximum luminance,in such a way that the maximum luminance in the expansion targetluminance range increases.

In the aspect of the video processor, it is preferable that theplurality of types of luminance-related information are formed ofmaximum luminance information representing maximum luminance of thevideo images and maximum average luminance information representing amaximum of average luminance values of frames that form the videoimages.

According to the aspect described above, the expansion target luminancerange can be determined by using a plurality of types ofluminance-related information written in Info Frame compliant with theHDMI standard.

In the aspect of the video processor, it is preferable that theplurality of types of luminance-related information are formed ofmaximum luminance information representing maximum luminance of thevideo images, maximum average luminance information representing amaximum of average luminance values of frames that form the videoimages, and point-of-editing maximum luminance information representingmaximum luminance of light from a display apparatus used when the videoimages are edited.

According to the aspect described above, the expansion target luminancerange can be determined by using the plurality of types ofluminance-related information written in Info Frame compliant with theHDMI standard.

In the aspect of the video processor, it is preferable that thereceiving section is capable of receiving the luminance-relatedinformation formed of a plurality of types of luminance-relatedinformation, that the plurality of types of luminance-relatedinformation include maximum luminance information representing maximumluminance of the video images, maximum average luminance informationrepresenting a maximum of average luminance values of frames that formthe video images, and point-of-editing maximum luminance informationrepresenting maximum luminance of light from a display apparatus usedwhen the video images are edited, and that when the receiving sectionreceives at least one of the maximum luminance information and themaximum average luminance information, the image processing sectiondetermines the expansion target luminance range based on the receivedinformation, whereas when the receiving section receives neither themaximum luminance information nor the maximum average luminanceinformation but receives the point-of-editing maximum luminanceinformation, the image processing section determines the expansiontarget luminance range based on the point-of-editing maximum luminanceinformation.

According to the aspect described above, as the luminance-relatedinformation used to determine the expansion target luminance range, themaximum luminance information and the maximum average luminanceinformation are allowed to have priority over the point-of-editingmaximum luminance information.

The maximum luminance information and the maximum average luminanceinformation change in accordance with the luminance of the video imagesthemselves, whereas the point-of-editing maximum luminance informationdoes not change with the luminance of the video images themselves butchanges with the maximum luminance that the video images can take on.Therefore, according to the aspect described above, theluminance-related information (maximum luminance information or maximumaverage luminance information) that is more likely to represent theluminance range of the video images than the point-of-editing maximumluminance information can be used to determine the expansion targetluminance range.

In the aspect of the video processor, it is preferable that, when thereceiving section does not receive the luminance-related information butreceives the video information, the image processing section determinesa pre-specified luminance range of the video images as the expansiontarget luminance range.

According to the aspect described above, even in a case where thereceiving section receives no luminance-related information, theexpansion target luminance range can be determined.

An aspect of a display apparatus according to the invention includes theimage processor described above and a display section that displaysvideo images according to the video information representing theexpansion target luminance range having been expanded.

According to the aspect described above, brighter, higher-contrast videoimages can be displayed than in a case where video images according tovideo information representing an expansion target luminance range thathas not been expanded are displayed.

An aspect of a video processing method according to the inventionincludes receiving video information representing video images andluminance-related information on luminance of the video images, anddetermining an expansion target luminance range of the video imagesbased on the luminance-related information and expanding the expansiontarget luminance range in such a way that maximum luminance in theexpansion target luminance range increases.

According to the aspect described above, since the expansion targetluminance range is so expanded that the maximum luminance in theexpansion target luminance range of the video images increases, theluminance range of the video images can be so broadened that the videoimages are brighter than in a case where the luminance range of thevideo images is not expanded. Further, since the expansion targetluminance range is determined on the basis of the luminance-relatedinformation, the expansion target luminance range can be changed inaccordance with the luminance-related information.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 shows a display apparatus according to a first embodiment thatadopts the invention.

FIG. 2 shows an example of a lookup table.

FIG. 3 shows an aspect of expansion of a luminance range in each mode.

FIG. 4 is a flowchart for describing the action of display apparatus inthe first embodiment.

FIG. 5 is a block diagram showing a display apparatus according to asecond embodiment.

FIG. 6 shows another example of the lookup table.

FIG. 7 is a flowchart for describing the action of a display apparatusaccording to the second embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments according to the invention will be described below withreference to the drawings. In the drawings, the dimension and scale ofeach portion differ from actual values as appropriate. Further, sincethe embodiments described below are preferable specific examples of theinvention, a variety of technically preferable restrictions are imposedon the embodiments. The scope of the invention is, however, not limitedto the restricted forms unless otherwise particularly stated in thefollowing description that a restriction is imposed on the invention.

First Embodiment

FIG. 1 shows a display apparatus 1 according to a first embodiment thatadopts the invention.

The display apparatus 1 is an HDR display apparatus that supports theHDR method and is, for example, a projector. A projector is currentlyrequired to display brightest possible video images. The requirement isnot limited to a projector and is common to other display apparatus.

The display apparatus 1 includes a video processor 10 and a displaysection 20. The brightness range of display operation performed by thedisplay section 20 corresponds to the range of luminance that HDR videoinformation compliant with the HDR method can take on (luminance rangefrom 0 to 10000 nit). The video processor 10 includes a receivingsection 11, an analyzing section 12, a storage section 13, and a videoprocessing section 14.

The receiving section 11 receives a signal compliant with the HDMIstandard (hereinafter referred to as “HDMI signal”) via an HDMI cable30.

The HDMI signal contains video information representing video images. Inthe following description, the video information contained in an HDMIsignal is referred to as “first video information,” and video imagesrepresented by the first video information are referred to as “firstvideo images.”

The HDMI signal further contains Info Frame. In the Info Frame iswritten luminance-related information on the luminance of the firstvideo images. Examples of the luminance-related information may includeMCLL (maximum content light level) information, MFaLL (maximumframe-average light level) information, and MaxDML (maximum displaymastering luminance) information.

The MCLL information is maximum luminance information representing themaximum luminance of the first video images. The MFaLL information ismaximum average luminance information representing the maximum ofaverage luminance values of the frames that form the first video images.The MaxDML information is point-of-editing maximum luminance informationrepresenting the maximum luminance of light from a display apparatusused when the first video images are edited.

EOTF (electro optical transfer function) information is further writtenin Info Frame. The EOTF information can be used as informationrepresenting whether the first video images comply with the HDR methodor an SDR (standard dynamic range) method.

The receiving section 11 supplies the analyzing section 12 with InfoFrame and supplies the video processing section 14 with the first videoinformation.

The analyzing section 12 analyzes Info Frame to read the informationwritten in Info Frame (luminance-related information and EOTFinformation, for example). The analyzing section 12 supplies the videoprocessing section 14 with the information read from Info Frame.

The storage section 13 stores a variety of pieces of information. Thestorage section 13 stores, for example, a lookup table LUT1 showing therelationship among the luminance-related information, an expansiontarget luminance range, and an expanded luminance range.

FIG. 2 shows an example of the lookup table LUT1.

The expansion target luminance range is a range taken as the dynamicrange of the luminance (range from minimum luminance to maximumluminance) of the first video images. The expansion target luminancerange is determined on the basis of the luminance-related information.

In FIG. 2, the MCLL information and the MFaLL information are used asthe luminance-related information.

In FIG. 2, the luminance-related information, the expansion targetluminance range, and the expanded luminance range are stored on a modebasis. For example, the MCLL information greater than or equal to 500nit but smaller than 1000 nit is related to the expansion targetluminance range greater than or equal to 0 nit but smaller than or equalto 1000 nit and the expanded luminance range greater than or equal to 0nit but smaller than or equal to 10000 nit. The MFaLL informationgreater than or equal to 400 nit but smaller than 800 nit is related tothe expansion target luminance range greater than or equal to 0 nit butsmaller than or equal to 2000 nit and the expanded luminance rangegreater than or equal to 0 nit but smaller than or equal to 10000 nit.

The video processing section 14 corrects the first video informationreceived from the receiving section 11 on the basis of theluminance-related information received from the analyzing section 12 togenerate second video information.

In the present embodiment, the video processing section 14 refers to thelookup table LUT1 and determines the expansion target luminance range ofthe first video images on the basis of the luminance-relatedinformation. The video processing section 14 then expands the expansiontarget luminance range to an expanded luminance range in such a way thatthe maximum luminance in the expansion target luminance range increasesto generate second video information having the expanded luminancerange.

The video processing section 14 supplies the display section 20 with thesecond video information. The display section 20 displays video imagesaccording to the second video information (hereinafter referred to as“second video images”).

A technical meaning of the action in which the video processor 10corrects the first video information to generate the second videoinformation will now be described.

The brightness range of display operation performed by the displaysection 20 corresponds to the range of luminance that HDR videoinformation can take on (luminance range from 0 to 10000 nit). The firstvideo information, however, does not necessarily represent video imageshaving the luminance of 10000 nit.

Consider now a case where the first video information is directlyinputted to the display section 20.

In this case, when the first video information represents video imagesthat do not have the luminance of 10000 nit, the display section 20 doesnot use the maximum brightness in the range of brightness that thedisplay section 20 can output. In detail, for example, in a case wherethe first video information represents video images having a maximumluminance of 1000 nit (video images compliant with UHD-BD standard), thedisplay section 20 does not use brightness values that belong to therange of brightness that the display section 20 can output andcorrespond to luminance values greater than 1000 nit but smaller than orequal to 10000 nit. Images displayed by the display section 20 aretherefore undesirably dark, low-contrast images.

To address the problem described above, in the present embodiment, theimage processing section 14 first refers to the lookup table LUT1 anddetermines the expansion target luminance range corresponding to theluminance-related information (range taken as dynamic range of luminanceof first video images). The image processing section 14 subsequentlyexpands the expansion target luminance range to an expanded luminancerange in such a way that the maximum luminance in the expansion targetluminance range is the maximum luminance (10000 nit) in the range ofluminance that HDR video information compliant with the HDR method cantake on to generate second video information. The image processingsection 14 then supplies the display section 20 with the second videoinformation.

The display section 20 therefore uses the maximum brightness in therange of brightness that the display section 20 can output to displaysecond video images according to the second video information. Thesecond video images are therefore brighter than the first video images.In this process, since the luminance range used to display the secondvideo images (expanded luminance range) is wider than the luminancerange used to represent the first video images, the second video imageshave contrast higher than that of the first video images.

As described above, in the present embodiment, the first videoinformation is not directly inputted to the display section 20, but thevideo processor 10 uses the first video information and theluminance-related information to generate the second video informationrepresenting the second video images that are brighter than the firstvideo images and have contrast higher than that of the first video imageand supplies the display section 20 with the second video information.

The maximum luminance in the expanded luminance range (10000 nit) is afixed value, as shown in FIG. 2, and equal to the maximum luminance inthe range of luminance that HDR video information can take on (10000nit). When the maximum luminance in the expanded luminance range isequal to the maximum luminance in the range of luminance that HDR videoinformation can take on, a highest-luminance video portion of the secondvideo images can be displayed by using the brightest portion of thebrightness range of display operation performed by the display section20. The second video images can therefore be brightest possible videoimages.

It is noted that the maximum luminance in the expanded luminance range(10000 nit) is an example of pre-specified target maximum luminancehigher than the maximum luminance in the expansion target luminancerange. The target maximum luminance may be lower than 10000 nit.

The image processing section 14 lowers the maximum luminance in theexpansion target luminance range by a greater amount when the luminancerepresented by the luminance-related information (MCLL information andMFaLL information shown in FIG. 2) is lower (see FIG. 2). This pointwill be described below.

The MCLL information represents the maximum in the dynamic range ofluminance of the first video images. The expansion target luminancerange is the range taken as the dynamic range of luminance of the firstvideo images. The image processing section 14 can therefore increase thedegree of coincidence between the expansion target luminance range andthe dynamic range of luminance of the first video images by lowering themaximum luminance in the expansion target luminance range by a greateramount when the luminance represented by the MCLL information is lower.

When a higher degree of coincidence between the expansion targetluminance range and the dynamic range of luminance of the first videoimages is achieved, second video information representing brighter,higher-contrast second video images can be generated with degradation inthe second video images due to the expansion of the luminance rangesuppressed.

The MFaLL information represents the maximum of average luminance valuesof the frames that form the first video images. It is anticipated thatthe lower the MFaLL information, the higher the probability of a smallmaximum in the dynamic range of luminance of the first video images.

The image processing section 14 can therefore increase the degree ofcoincidence between the expansion target luminance range and the dynamicrange of luminance of the first video images by lowering the maximumluminance in the expansion target luminance range by a greater amountwhen the luminance represented by the MFaLL information is lower. Secondvideo information representing brighter, higher-contrast second videoimages can therefore be generated with degradation in the second videoimages due to the expansion of the luminance range suppressed, asdescribed above.

The image processing section 14 has six modes, specifically, an HDR0mode to an HDR4 mode and an SDR mode. The SDR mode is a modecorresponding to the SDR method. The action of the image processingsection 14 in the SDR mode is known and will not therefore be describedin detail. The HDR0 to HDR4 modes are modes corresponding to the HDRmethod. FIG. 3 shows the relationship among the HDR0 to HDR4 modes, theexpansion target luminance range, and the expanded luminance range.

In the HDR0 to HDR3 modes, the process of expanding the luminance rangeof the first video images is carried out, as shown in FIGS. 2 and 3.

The HDR0 mode is a mode used when the expansion target luminance range(range taken as dynamic range of luminance of first video images) isdetermined to be “greater than or equal to 0 nit but smaller than orequal to 500 nit” on the basis of the luminance-related information(MCLL information or MFaLL information).

In the HDR0 mode, the image processing section 14 generates the secondvideo information by expanding the expansion target luminance range ofthe first video images that is “greater than or equal to 0 nit butsmaller than or equal to 500 nit” (maximum luminance of 500 nit) to anexpanded luminance range that is “greater than or equal to 0 nit butsmaller than or equal to 10000 nit” (target maximum luminance of 10000nit). In the HDR0 mode, the maximum luminance of 500 nit in theexpansion target luminance range of the first video images is convertedinto the target maximum luminance of 10000 nit.

The degree of expansion of the expansion target luminance range in theHRD0 mode is 20 times. In the HDR0 mode, the image processing section 14generates the second video information by correcting the portion of thefirst video images that has luminance that belongs to the expansiontarget luminance range “greater than or equal to 0 nit but smaller thanor equal to 500 nit” in such a way that the luminance is multiplied by20 and correcting the portion of the first video images that hasluminance that does not belong to the expansion target luminance range“greater than or equal to 0 nit but smaller than or equal to 500 nit” insuch a way that the luminance is uniformly changed to 10000 nit.

The method for generating the second video information in the HDR0 modeis not limited to the method described above and can be changed asappropriate.

The HDR1 mode is a mode used when the expansion target luminance range(range taken as dynamic range of luminance of first video images) isdetermined to be “greater than or equal to 0 nit but smaller than orequal to 1000 nit” on the basis of the luminance-related information(MCLL information or MFaLL information).

In the HDR1 mode, the image processing section 14 generates the secondvideo information by expanding the expansion target luminance range ofthe first video images that is “greater than or equal to 0 nit butsmaller than or equal to 1000 nit” (maximum luminance of 1000 nit) to anexpanded luminance range that is “greater than or equal to 0 nit butsmaller than or equal to 10000 nit” (target maximum luminance of 10000nit). In the HDR1 mode, the maximum luminance of 1000 nit in theexpansion target luminance range of the first video images is convertedinto the target maximum luminance of 10000 nit.

The degree of expansion of the expansion target luminance range in theHRD1 mode is 10 times. In the HDR1 mode, the image processing section 14generates the second video information by correcting the portion of thefirst video images that has luminance that belongs to the expansiontarget luminance range “greater than or equal to 0 nit but smaller thanor equal to 1000 nit” in such a way that the luminance is multiplied by10 and correcting the portion of the first video images that hasluminance that does not belong to the expansion target luminance range“greater than or equal to 0 nit but smaller than or equal to 1000 nit”in such a way that the luminance is uniformly changed to 10000 nit.

The method for generating the second video information in the HDR1 modeis not limited to the method described above and can be changed asappropriate.

The HDR2 mode is a mode used when the expansion target luminance range(range taken as dynamic range of luminance of first video images) isdetermined to be “greater than or equal to 0 nit but smaller than orequal to 2000 nit” on the basis of the luminance-related information.

In the HDR2 mode, the image processing section 14 generates the secondvideo information by expanding the expansion target luminance range ofthe first video images that is “greater than or equal to 0 nit butsmaller than or equal to 2000 nit” (maximum luminance of 2000 nit) to anexpanded luminance range that is “greater than or equal to 0 nit butsmaller than or equal to 10000 nit” (target maximum luminance of 10000nit). In the HDR2 mode, the maximum luminance of 2000 nit in theexpansion target luminance range of the first video images is convertedinto the target maximum luminance of 10000 nit.

The degree of expansion of the expansion target luminance range in theHRD2 mode is 5 times. In the HDR2 mode, the image processing section 14generates the second video information by correcting the portion of thefirst video images that has luminance that belongs to the expansiontarget luminance range “greater than or equal to 0 nit but smaller thanor equal to 2000 nit” in such a way that the luminance is multiplied by5 and correcting the portion of the first video images that hasluminance that does not belong to the expansion target luminance range“greater than or equal to 0 nit but smaller than or equal to 2000 nit”in such a way that the luminance is uniformly changed to 10000 nit.

The method for generating the second video information in the HDR2 modeis not limited to the method described above and can be changed asappropriate.

The HDR3 mode is a mode used when the expansion target luminance range(range taken as dynamic range of luminance of first video images) isdetermined to be “greater than or equal to 0 nit but smaller than orequal to 4000 nit” on the basis of the luminance-related information.

In the HDR3 mode, the image processing section 14 generates the secondvideo information by expanding the expansion target luminance range ofthe first video images that is “greater than or equal to 0 nit butsmaller than or equal to 4000 nit” (maximum luminance of 4000 nit) to anexpanded luminance range that is “greater than or equal to 0 nit butsmaller than or equal to 10000 nit” (target maximum luminance of 10000nit). In the HDR3 mode, the maximum luminance of 4000 nit in theexpansion target luminance range of the first video images is convertedinto the target maximum luminance of 10000 nit.

The degree of expansion of the expansion target luminance range in theHRD3 mode is 2.5 times. In the HDR3 mode, the image processing section14 generates the second video information by correcting the portion ofthe first video images that has luminance that belongs to the expansiontarget luminance range “greater than or equal to 0 nit but smaller thanor equal to 4000 nit” in such a way that the luminance is multiplied by2.5 and correcting the portion of the first video images that hasluminance that does not belong to the expansion target luminance range“greater than or equal to 0 nit but smaller than or equal to 4000 nit”in such a way that the luminance is uniformly changed to 10000 nit.

The method for generating the second video information in the HDR3 modeis not limited to the method described above and can be changed asappropriate.

The HDR4 mode is a mode used when the expansion target luminance range(range taken as dynamic range of luminance of first video images) isdetermined to be “greater than or equal to 0 nit but smaller than orequal to 10000 nit” on the basis of the luminance-related information.

In the HDR4 mode, the image processing section 14 generates the secondvideo information by expanding the expansion target luminance range ofthe first video images that is “greater than or equal to 0 nit butsmaller than or equal to 10000 nit” (maximum luminance of 10000 nit) toan expanded luminance range that is “greater than or equal to 0 nit butsmaller than or equal to 10000 nit” (target maximum luminance of 10000nit).

The degree of expansion of the expansion target luminance range in theHRD4 mode is 1 times. In the HDR4 mode, since the expansion factor ofthe luminance range is 1, the luminance range of the first video imagesthat is “greater than or equal to 0 nit but smaller than or equal to10000 nit” substantially functions as a “luminance range to bemaintained” instead of the expansion target luminance range.

The degrees of expansion in the HDR0, HDR1, HDR2, HDR3, and HDR4 modesare not limited to 20, 10, 5, 2.5, and 1, respectively, and can bechanged as appropriate to the extent that the degree of expansiondecreases in the order of the HDR0, HDR1, HDR2, HDR3, and HDR4 modes.

The action of the display apparatus in the first embodiment will next bedescribed.

FIG. 4 is a flowchart for describing the action of the display apparatusin the first embodiment.

The receiving section 11, when it receives an HDMI signal (step S401),supplies the analyzing section 12 with Info Frame contained in the HDMIsignal and supplies the image processing section 14 with the first videoinformation contained in the HDMI signal.

The analyzing section 12 analyzes Info Frame and reads informationwritten in Info Frame. The analyzing section 12 supplies the videoprocessing section 14 with the information read from Info Frame.

The image processing section 14, when it receives the information fromthe analyzing section 12, evaluates whether the first video imagescomply with the HDR method or the SDR method on the basis of the EOTFinformation, which is part of the received information (step S402).

In the case where the first video images comply with the HDR method, theimage processing section 14 refers to the lookup table LUT1 anddetermines, as a first mode candidate, an HDR mode corresponding to theMCLL information, which is part of the information received from theanalyzing section 12 (step S403). In a case where no MCLL information ispresent in the information received from the analyzing section 12, theimage processing section 14 skips through step S403.

The image processing section 14 subsequently refers to the lookup tableLUT1 and determines, as a second mode candidate, an HDR modecorresponding to the MFaLL information received from the analyzingsection 12 (step S404). In a case where no MFaLL information is presentin the information received from the analyzing section 12, the imageprocessing section 14 skips through step S404.

The image processing section 14 subsequently evaluates whether or notneither MCLL information nor MFaLL information is present in theinformation received from the analyzing section 12 (step S405).

In the case where neither MCLL information nor MFaLL information ispresent in the information received from the analyzing section 12 (Yesin step S405), the image processing section 14 selects a default HDRmode as the mode to be used (step S406). It is assumed in the followingdescription that the HDR2 mode has been specified in advance as thedefault HDR mode. The default HDR mode is not limited to the HDR2 modeand can be changed as appropriate.

On the other hand, in a case where the MCLL information and the MFaLLinformation are both present in the information received from theanalyzing section 12 (No in step S405), the image processing section 14selects one of the first mode candidate and the second mode candidate,the mode candidate in which the maximum luminance in the expansiontarget luminance range corresponding to the mode candidate is lower, asa mode to be used (step S407).

In a case where the maximum luminance in the expansion target luminancerange corresponding to the first mode candidate is equal to the maximumluminance in the expansion target luminance range corresponding to thesecond mode candidate, that is, in a case where the first mode candidateand the second mode candidate are the same HDR mode, the imageprocessing section 14 selects the same HDR mode as the mode to be used.

Another situation in which a result of the evaluation in step S405 showsNo is conceivably a case where only one of the MCLL information and theMFaLL information is present in the information received from theanalyzing section 12. In this case, since one of steps S403 and S404 hasbeen carried out, one of the first and second mode candidates has beendetermined as the mode to be used. The image processing section 14therefore selects the determined one of the first and second modecandidates as the mode to be used.

In the case where the first video images comply with the SDR method instep S402, the image processing section 14 selects the SDR mode as themode to be used (step S408).

Having selected the mode to be used (step S406, S407, or S408), theimage processing section 14 uses the selected mode to generate thesecond video information (step S409). The method for generating thesecond video information in each of the HDR0 to HDR4 modes has beendescribed above. Further, the method for generating the second videoinformation in the SDR mode is a known technology and will not thereforebe described.

The image processing section 14 subsequently supplies the displaysection 20 with the second video information. The display section 20displays second video images on the basis of the second videoinformation (step S410).

According to the present embodiment, the image processing section 14generates the second video information representing the second videoimages by expanding the expansion target luminance range of the firstvideo images in such a way that the maximum luminance in the expansiontarget luminance range of the first video images increases. The secondvideo images can thus be brighter than the first video images and havecontrast higher than that of the first video images.

Further, the image processing section 14 selects a mode candidate foreach of the MCLL information and the MFaLL information. In the HDR modesused as the mode candidates, the expansion target luminance range hasbeen determined on an HDR mode basis. The selection of a mode candidatefor each of the MCLL information and the MFaLL information thereforemeans determination of the expansion target luminance range on aluminance-related information basis.

The image processing section 14 then selects one of the first and secondmode candidates, the mode candidate in which the maximum luminance inthe corresponding expansion target luminance range is lower, as the modeto be used and uses the selected mode to generate the second videoinformation. The process described above means that the image processingsection 14 generates the second video information by expanding one ofthe expansion target luminance ranges provided on a luminance-relatedinformation basis, the expansion target luminance range having lowermaximum luminance in such a way that the maximum luminance in theexpansion target luminance range having the lower maximum luminanceincreases.

The process described above allows the second video images to bebrighter and the contrast of the second video images to be higher thanin a case where the second video information is generated by expandingthe expansion target luminance range having the higher maximumluminance.

Further, when the receiving section 11 receives no luminance-relatedinformation but receives the first video information, that is, when aresult of the evaluation in step S405 shown in FIG. 4 shows Yes, theimage processing section 14 selects the default HDR mode as the mode tobe used and uses the selected mode to generate the second videoinformation.

Therefore, even when the receiving section 11 receives noluminance-related information, the expansion target luminance range canbe determined, and the luminance range can be expanded.

Second Embodiment

In the first embodiment, the MCLL information and the MFaLL informationare used as the luminance-related information.

In a second embodiment, the MaxDML information is further used as theluminance-related information. The MaxDML information is used to selecta mode to be used in the case where neither the MCLL information nor theMFaLL information is written in Info Frame.

FIG. 5 shows a display apparatus 1A according to the second embodimentthat adopts the invention. In FIG. 5, the same configurations as thoseshown in FIG. 1 have the same reference characters.

The display apparatus 1A according to the second embodiment differs fromthe display apparatus 1 according to the first embodiment in that avideo processor 10A is provided in place of the video processor 10. Thedisplay apparatus 1A according to the second embodiment will bedescribed below primarily on differences from the display apparatus 1according to the first embodiment.

The video processor 10A differs from the video processor 10 shown inFIG. 1 in that the video processor 10A includes a storage section 13A inplace of the storage section 13 and a video processing section 14A inplace of the video processing section 14.

The storage section 13A stores a lookup table LUT2 shown in FIG. 6 inaddition to the lookup table LUT1 shown in FIG. 2. In the lookup tableLUT2, the MaxDML information, which is luminance-related information,the expansion target luminance range of the first video images, and theexpanded luminance range thereof are related to one another on an HDRmode basis (for each of HDR0 to HDR4 modes). For example, the MaxDMLinformation greater than or equal to 2000 nit but smaller than 4000 nitis related to the expansion target luminance range greater than or equalto 0 nit but smaller than or equal to 4000 nit and the expandedluminance range greater than or equal to 0 nit but smaller than or equalto 10000 nit.

When the receiving section 11 receives at least one of the MCLLinformation and the MFaLL information, the image processing section 14Arefers to the lookup table LUT1 and determines the expansion targetluminance range on the basis of the received information. Thedetermination method is the same method described in the firstembodiment.

When the receiving section 11 receives neither the MCLL information northe MFaLL information but receives the MaxDML information, the imageprocessing section 14A refers to the lookup table LUT2 and determinesthe expansion target luminance range corresponding to the MaxDMLinformation.

The action of the display apparatus in the second embodiment will nextbe described.

FIG. 7 is a flowchart for describing the action of the video processor10A in the second embodiment. In FIG. 7, the same processes as thoseshown in FIG. 4 have the same reference characters. The action of thedisplay apparatus in the second embodiment will be described primarilyon processes different from those shown in FIG. 4.

When a result of the evaluation in step S405 is Yes, that is, whenneither MCLL information nor the MFaLL information is present in theinformation received from the analyzing section 12, the video processingsection 14A evaluates whether or not the MaxDML information is presentin the information received from the analyzing section 12 (step S701).

In the case where no MaxDML information is present in the informationreceived from the analyzing section 12 (Yes in step S701), the videoprocessing section 14A carries out step S406.

On the other hand, in the case where the MaxDML information is presentin the information received from the analyzing section 12 (No in stepS701), the video processing section 14A refers to the lookup table LUT2and determines an HDR mode corresponding to the MaxDML information asthe mode to be used (step S702).

When the HDR mode is determined, the expansion target luminance rangeused in the HDR mode is uniquely determined. The determination of an HDRmode corresponding to the MaxDML information as the mode to be usedtherefore means determination of the expansion target luminance range onthe basis of the MaxDML information.

Having determined the mode to be used, the video processing section 14Acarries out step S409.

According to the present embodiment, as the luminance-relatedinformation used to determine the expansion target luminance range, theMCLL information and the MFaLL information are allowed to have priorityover the MaxDML information.

The MCLL information and the MFaLL information change in accordance withthe luminance of the first video images themselves, whereas the MaxDMLinformation does not change with the luminance of the first video imagesthemselves but changes with the maximum luminance that the luminance ofthe first video images can take on.

Therefore, in the present embodiment, the MCLL information or the MFaLLinformation, which is more likely to represent the luminance range ofthe first video images than the MaxDML information, is used to determinethe expansion target luminance range. The degree of coincidence betweenthe expansion target luminance range and the dynamic range of luminanceof the first video images can therefore be increased.

When a higher degree of coincidence between the expansion targetluminance range and the dynamic range of luminance of the first videoimages is achieved, second video information representing brighter,higher-contrast second video images can be generated with degradation inthe second video images due to the expansion of the luminance rangesuppressed.

Variations

The embodiments described above can be changed in a variety of manners.Specific aspects of the variations will be presented below by way ofexample. Two or more aspects arbitrarily selected from the followingexamples can be merged into one aspect as appropriate to the extent thatthe selected aspects do not contradict each other.

Variation 1

In the first embodiment, the image processing section 14 selects, as theexpansion target luminance range, one of an expansion target luminancerange determined on the basis of the MCLL information (hereinafterreferred to as “first candidate”) and an expansion target luminancerange determined on the basis of the MFaLL information (hereinafterreferred to as “second candidate”), that is, the expansion targetluminance range having lower maximum luminance.

The image processing section 14 may select, as the expansion targetluminance range, one of the first candidate, the second candidate, andthe expansion target luminance range determined on the basis of theMaxDML information (hereinafter referred to as “third candidate”), thatis, the expansion target luminance range having the lowest maximumluminance.

Variation 2

In the second embodiment, in the case where none of the two pieces ofinformation described above, neither the MCLL information nor the MFaLLinformation, is present, the video processing section 14A determines themode to be used on the basis of the MaxDML information.

Conversely, the video processing section 14A may allow the MaxDMLinformation to have priority over the MCLL information and the MFaLLinformation, and in the case where no MaxDML information is present, thevideo processing section 14A may determine the mode to be used on thebasis of the MCLL information or the MFaLL information.

Variation 3

The number of modes is not limited to five and can be changed asappropriate. The values shown in the lookup tables LUT1 and LUT2 can bechanged as appropriate.

Variation 4

In each of the embodiments described above, the expansion targetluminance range is changed stepwise on the basis of theluminance-related information. The expansion target luminance range mayinstead be linearly changed on the basis of the luminance-relatedinformation.

Variation 5

In step S407, at least one of the video processing sections 14 and 14Amay select, as the mode to be used, one of the first mode candidate andthe second mode candidate, the mode candidate in which the maximumluminance in the expansion target luminance range corresponding to themode candidate is higher, instead of the mode candidate in which themaximum luminance is lower.

This process means that at least one of the video processing sections 14and 14A generates the second video information by expanding one of theexpansion target luminance ranges provided on a luminance-relatedinformation basis, the expansion target luminance range having highermaximum luminance in such a way that the maximum luminance in theexpansion target luminance range having the higher maximum luminanceincreases.

In this case, saturation of luminance due to the expansion of theluminance range can be suppressed, as compared with the case where thesecond video information is generated by expanding the expansion targetluminance range having lower maximum luminance.

Variation 6

The order in accordance with which the processes in step S403 and stepS404 are carried out may be swapped.

Variation 7

Step S405 may be carried out before step S403. In this case, when aresult of the evaluation in step S405 shows No, step S403 is carriedout, and step S407 is carried out after step S404.

Variation 8

In each of the embodiments described above, an HDMI signal is used asthe signal containing the first video data and the luminance-relatedinformation, but the signal containing the first video data and theluminance-related information is not limited to an HDMI signal and canbe changed as appropriate.

Variation 9

At least one of the image processors 10 and 10A may not be integratedwith the display section 20 and may be separate therefrom.

Variation 10

At least one of the display apparatus 1 and 1A is not limited to aprojector and can be changed as appropriate. For example, the displayapparatus 1 may be a liquid crystal display apparatus (LCD). In thiscase, the display section 20 has a display screen and displays videoimages on the display screen.

Variation 11

Entirety or part of the video processing sections 14, 14A and theanalyzing section 12 may be achieved by using a dedicated electroniccircuit or may be achieved by a CPU or any other computer that reads aprogram from a computer readable recording medium and executes theprogram.

What is claimed is:
 1. A video processing method comprising: receivingvideo information representing video images and luminance-relatedinformation on luminance of the video images, the luminance-relatedinformation being formed of a plurality of types of luminance-relatedinformation; and determining an expansion target luminance range of thevideo images for each of the types of luminance-related informationbased on the luminance-related information and expanding one of theexpansion target luminance range for the types of the luminance-relatedinformation, the one of the expansion target luminance range havinglowest maximum luminance, in such a way that the maximum luminance inthe expansion target luminance range having the lowest maximum luminanceincreases.
 2. The video processing method according to claim 1, whereinthe expansion target luminance range is expanded in such a way that themaximum luminance in the expansion target luminance range is equal topre-specified target maximum luminance higher than the maximumluminance.
 3. The video processing method according to claim 2, whereinthe maximum luminance is lowered in the expansion target luminance rangeby a greater amount when luminance represented by the luminance-relatedinformation is lower.
 4. The video processing method according to claim1, wherein the plurality of types of luminance-related information areformed of maximum luminance information representing maximum luminanceof the video images and maximum average luminance informationrepresenting a maximum of average luminance values of frames that formthe video images.
 5. The video processing method according to claim 1,wherein the plurality of types of luminance-related information areformed of maximum luminance information representing maximum luminanceof the video images, maximum average luminance information representinga maximum of average luminance values of frames that form the videoimages, and point-of-editing maximum luminance information representingmaximum luminance of light from a display apparatus used when the videoimages are edited.
 6. A video processing method comprising: receivingvideo information representing video images and luminance-relatedinformation on luminance of the video images, the luminance-relatedinformation being formed of a plurality of types of luminance-relatedinformation; and determining an expansion target luminance range of thevideo images for each of the types of luminance-related informationbased on the luminance-related information and expanding one of theexpansion target luminance range for the types of the luminance-relatedinformation, the one of the expansion target luminance range havinghighest maximum luminance, in such a way that the maximum luminance inthe expansion target luminance range having the highest maximumluminance increases.
 7. The video processing method according to claim6, wherein the expansion target luminance range is expanded in such away that the maximum luminance in the expansion target luminance rangeis equal to pre-specified target maximum luminance higher than themaximum luminance.
 8. The video processing method according to claim 7,wherein the maximum luminance is lowered in the expansion targetluminance range by a greater amount when luminance represented by theluminance-related information is lower.
 9. The video processing methodaccording to claim 6, wherein the plurality of types ofluminance-related information are formed of maximum luminanceinformation representing maximum luminance of the video images andmaximum average luminance information representing a maximum of averageluminance values of frames that form the video images.
 10. The videoprocessing method according to claim 6, wherein the plurality of typesof luminance-related information are formed of maximum luminanceinformation representing maximum luminance of the video images, maximumaverage luminance information representing a maximum of averageluminance values of frames that form the video images, andpoint-of-editing maximum luminance information representing maximumluminance of light from a display apparatus used when the video imagesare edited.
 11. A video processing method comprising: receiving videoinformation representing video images and luminance-related informationon luminance of the video images, the luminance-related informationbeing formed of a plurality of types of luminance-related information;and determining an expansion target luminance range of the video imagesbased on the luminance-related information and expanding the expansiontarget luminance range in such a way that maximum luminance in theexpansion target luminance range increases, wherein the plurality oftypes of luminance-related information include maximum luminanceinformation representing maximum luminance of the video images, maximumaverage luminance information representing a maximum of averageluminance values of frames that form the video images, andpoint-of-editing maximum luminance information representing maximumluminance of light from a display apparatus used when the video imagesare edited, and when at least one of the maximum luminance informationand the maximum average luminance information is received, the expansiontarget luminance range is determined based on the received information,when neither the maximum luminance information nor the maximum averageluminance information is received but the point-of-editing maximumluminance information is received, the expansion target luminance rangeis determined based on the point-of-editing maximum luminanceinformation.
 12. The video processing method according to claim 11,wherein the expansion target luminance range is expanded in such a waythat the maximum luminance in the expansion target luminance range isequal to pre-specified target maximum luminance higher than the maximumluminance.
 13. The video processing method according to claim 12,wherein the maximum luminance is lowered in the expansion targetluminance range by a greater amount when luminance represented by theluminance-related information is lower.